((a)) Funds available for forest development roads and trails shall be used by the Secretary of Agriculture to pay for the costs of construction and maintenance thereof, including roads and trails on experimental and other areas under Forest Service administration. In connection therewith, the Secretary of Agriculture may enter into contracts with a State or civil subdivision thereof, and issue such regulations as he deems advisable.
((b)) Cooperation of States, counties, or other local subdivisions may be accepted but shall not be required by the Secretary of Agriculture.
((c)) Construction estimated to cost $50,000 or more per mile or $50,000 or more per project for projects with a length of less than one mile, exclusive of bridges and engineering, shall be advertised and let to contract. If such estimated cost is less than $50,000 per mile or $50,000 per project for projects with a length of less than one mile or if, after proper advertising, no acceptable bid is received or the bids are deemed excessive, the work may be done by the Secretary of Agriculture on his own account.
((d)) Funds available for forest development roads and trails shall be available for adjacent vehicular parking areas, which may include electric vehicle charging stations or natural gas vehicle refueling stations, and for sanitary, water, and fire control facilities.